1. Technical Field
The subject matter described herein relates to systems, apparatuses, and methods for inserting dither samples that are independent of data resolution into audio signals and transmissions.
2. Background Art
Data transmission on audio channels occurs between audio transmitters and audio receivers. Audio transmitters, such as set-top boxes (e.g., cable/satellite set-top boxes), provide audio signals to audio receivers, such as televisions and/or other home theater devices. In order to save power, audio receivers typically enter a power saving mode when no data (i.e., silence or an inactive data stream) is transmitted the audio transmitters. The audio receivers resume a normal mode of operation when data resumes in the received data stream (i.e., sound or an active data stream). However, audio receivers may become unsynchronized with audio transmitters during the power saving mode. For instance, during a power saving mode, audio receivers may stop tracking the clock signal provided with the audio data from the audio transmitter. When an audio receiver fails to track the clock, synchronization with an audio transmitter may be lost, and when the audio receiver comes out of its power saving mode, the transmitter clock must be re-acquired by the audio receiver to recapture synchronization. The process of re-acquiring synchronization often results in unpleasing noise such as pops, clicks, and/or static at the audio receiver. Additionally, re-acquiring synchronization requires additional delay and consumption of processor cycles.
In the current state of the art, a dither sample is provided to an audio receiver from an audio transmitter during periods in which only silence is transmitted to the audio receiver. In prior solutions, a dither sample usually is a data value that is the smallest possible positive data value that may be transmitted to an audio receiver so that resulting audio that is broadcast based on the dither sample is of a low amplitude. Typically, data is transmitted from audio transmitters in a 1's complement or 2's complement format, and therefore, dither samples typically have a value of ‘1’ (usually in hexadecimal representation) regardless of the bit resolution of the transmission. For example, a 16-bit resolution dither sample with value ‘1’ is 0001h, and a 24-bit resolution dither sample with value ‘1’ is 000001h. However, when the audio transmitter has a higher bit resolution than the audio receiver, such a dither sample may not be received by the audio receiver. For instance, a 24-bit audio transmitter may provide audio data to a 20-bit or 16-bit audio receiver. In these cases, the audio transmitter provides 24-bit dither samples of 000001h, but because of their lower bit resolutions, 20-bit and 16-bit audio receivers truncate the dither samples (one or more right-most bits are lost). In a 20-bit resolution audio receiver, a 24-bit dither sample of 000001h is received as 00000h, and in a 16-bit resolution audio receiver, a 24-bit dither sample of 000001h is received as 0000h. Consequently, the dither sample is not received in these cases, and the 20-bit and 16-bit audio receivers effectively receive silence (no data or inactive data streams) and go into power saving modes where synchronization is lost.
Similarly, a 24-bit audio receiver may receive audio data from a 20-bit or 16-bit audio transmitter. A dither value of ‘0001h’ (16-bit) or a dither value of ‘00001h’ (20-bit) will be received as higher amplitude values by the 24-bit audio receiver: ‘000100h’ and ‘000010h’ respectively.